Adaptor Design Pattern example using PHP

Adapters are used to enable objects with different interfaces to communicate with each other.Convert the interface of a class into another interface clients expect. It is useful when we upgrade system

<?php
//SimpleBook.php copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
 
class SimpleBook
{
     private $author;
     private $title;
     function __construct($author_in, $title_in) {
        $this->author = $author_in;
        $this->title  = $title_in;
    }
    function getAuthor() {return $this->author;}
    function getTitle() {return $this->title;}
}
?>

<?php
//BookAdapter.php copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
include_once('SimpleBook.php');

class BookAdapter
{
    private $book;
    function __construct(SimpleBook $book_in) {
      $this->book = $book_in;
    }
    function getAuthorAndTitle() {
      return $this->book->getTitle() . ' by ' . $this->book->getAuthor();
    }
}
?>

<?php
//testAdapter.php copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
include_once('SimpleBook.php');
include_once('BookAdapter.php');

define('BR', '<'.'BR'.'>');
echo 'BEGIN TESTING ADAPTER PATTERN'.BR;
echo BR;

$book = new SimpleBook("Gamma, Helm, Johnson, and Vlissides","Design Patterns");
$bookAdapter = new BookAdapter($book);
echo 'Author and Title: '.$bookAdapter->getAuthorAndTitle();
echo BR.BR;
echo 'END TESTING ADAPTER PATTERN'.BR;
?>

Source: From lecture notes of Design and Development Open Multi-tier Application